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Hrvatsko asfaltersko društvo Croatian asphalt association
Raziličite tehonologije hladnog in-situ recikliranja u Europi i orgraničenja uvjetovana
stanjima cesteVariety of cold-in-place recycling technologies
within Europe and limits regarding varyingroad conditions
Konrad Mollenhauer, Uni Kassel
Međunarodni seminar ASFALTNI KOLNICI 2017International seminar ASPHALT PAVEMENTS 2017
Opatija, 05.– 06. 04. 2017.
• Cold recycling mixtures vary considerable in
Europe
• Binder types
• Bitumen emulsion
• Foamed bitumen
• Cement
• Binder contents
• Mix design procedures
• Laboratory Compaction methods
• Accelerated Curing procedures
• Mechanical test methods
• Specification values
• Project aim: Prepare harmonisation process
Cold Recycling Technologies in Europe: CoRePaSol-Project
Characterization of advanced cold
recycled bitumen stabilized
pavement solutions
Project funded by CEDR
2013-2014
Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 2
• Cold Recycling-Technologies in Europe
• Construction procedure
• Variety of mix concepts
• Effect of mix composition
• Proposal for mix design
• Limits regarding varying road conditions
• Results of laboratory project
• Recommendations
Content of presentation
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 3
Cold Recycling: Mix and constrcution procedures
1. Milling / Granulation of existing
pavement
2. Mixing crushed pavement
material (in situ or in plant)
• Bituminous binder (bitumenemulsion or foamed bitumen)
• Cement (mineral binder oractive filler)
• Additional aggregates toadjust grading
3. Paving
4. Compaction
5. Construction of surface layer(s)
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 4
• Mixing and compaction at ambient temperatures require addition of water
• Water results in high voids content and reduced bearing capacity after construction and
has to be removed from the layer:
Evaporation/Drainage in warm climate – Addition of cement in moist climate
Cold recycled road materials: Variety of mixes
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 5
Collings et al., 2009
Cold recycled road materials: Variety of mixes
Type and degree of bonding
affects:
• Visco-ealsticity / stiffness
• Curing time
• Cracking / rutting resistance
• Water sensitivity
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 6
1. Pre-assessment of mix granulate
• Continuous grading (concrete type)
• Assessment of optimum moisture content (mod. Proctor)
2. Selection of binder content range
• BSM for dry climate or soft subground (only with foamed bitumen)
• CBSM for moist climate
3. Compaction of specimens for mechanical tests
4. Laboratory curing
• BSM: 3 days oven drying @ 50 °C
• CBSM: 28 days at room conditions
5. Specimen assessment
• Void content (the lower the better)
• Stiffness
• Strength (e. g. Indirect tensile tests - ITS)
both properties: higher values are better – however, not to be reached by excess addition of cement
CoRePaSol: Proposed (harmonised) mix design procedure
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 7
60 60
d0
d0
d60
d60
• Homogeneity of reclaimed asphalt is a
predominating property controlling the hot
recycling process
• Nomograms for allowed RA contents are available
• RA content results of homogeneity of RA properties and allowed tolerances within mix composition (binder content, grading, …)
• For cold recycling, effects of non-homogeneious
pavements are not known
• Changing structural properties are obstancles for
Cold recycling (especially: cold-in-place)
• Research question (within CoRePaSol-project):
• What are the limits of homogeneities for cold recycling process?
• What is the effect of (aged) bitumen in recycled asphalt within cold recycling mixtures?
Limits for varying pavement conditions for cold recycling
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 8
Limits for varying pavement conditions for cold recycling
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 9
• Conditions of pavement to be
rehabilitated can vary
• „grown“ road with multiple maintenances during last centuries/decades
• Road widening on one side
• Small repair sections
• Varying parameters:
• Layers (materials)
• Thickness
• Conditions
• In given milling horizon:
• Asphalt layers
• Hydraulically bound layers
• Unbound layers
• Transversal and longitudinal
differences
0
10
20
30
40
50
60
70
80
Pav
emen
t d
epth
[cm
]
SMA AC B AC T Cement Base Unbound Subbase
0
10
20
30
40
50
60
70
80
Pav
emen
t d
epth
[cm
]
BSM Unbound Subbase
• Reclaimed asphalt 0/16
• Binder content: 5.4 %,
• TR&B: 63.5°C,
• Pen 23 1/10 mm
• Reclaimed road concrete 0/22
• Basaltic aggregates (to simulate reclaimed
unbound base)
• Mix design (BCSM):
• Addition of 3,6 % limestone filler to adjust grading
• 4 % added bitumen content
a) Foamed bitumen 50/70
b) Bitumen emulsion
• 2 % cement
• Moisture content: 7,8 %
Laboratory study: Effect of mix granulate composition on cold recycled material
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 10
0
10
20
30
40
50
60
70
80
90
100
0,0
62
5
0,1
25
0,2
5
0,5 1 2 4 8
16
32
pa
ssin
g [%
]sieve [mm]
Mix designReclaimed asphaltReclaimed road concrete
Selection of mix variations
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 11
• 100 %
reclaimed
asphalt
• Reclaimed
asphalt +
unbound base
• Reclaimed
asphalt +
reclaimed road
concrete
• Reclaimed
asphalt +
reclaimed road
concrete +
unbound base
Mix
variations
Reclaimed
asphalt
(RA)
Reclaimed
road
concrete
(RRC)
Unbound
material
(unb.)
A 100/0/0 96,4 - 3,6
B 75/0/25 77,1 22,9
C 50/25/25 48,2 25,0 26,8
D 50/0/50 48,2 - 51,8
E 40/20/40 38,6 20,0 41,4
F 0/50/50 - 50,0 50,0
G 0/25/75 25,0 75,0
H 0/0/100 - - 100,0
Laboratory study: Effect of mix granulate composition on cold recycled material
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 12
0% 50% 100%
A 100/0/0
B 75/0/25
C 50/25/25
D 50/0/50
E 40/20/40
F 0/50/50
G 0/25/75
H 0/0/100
Mix granulate compositions
Reclaimed asphalt
Reclaimed road concrete
Unbound Aggregates
Cold recycling mix composition and test program
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | ‹Nr.›
Test program:
• Static compaction (30 s á 45.9 kN)
• Specimen curing:
• 1 day in mould
• 2 days in mould (~ 20 °C)
• 25 days at room conditions
• Tests
• Bulk density & void content
• Indirect tensile strength (5 °C)
• Water sensitivity (ITS dry vs. 14 days in water)
• CBRdry (California Bearing Ratio)
Mix preparation
Specimen curingITS CBR
Results: Void content after 28 days of (dry) curing at room conditions
• Comparably high void contents
• Low compaction energy (lowercompared to field compaction)
• Coarse mix with low finescontent
• Mixtures containing RA are
better to compact compared to
mixtures without RA
• Little effect of reclaimed road
concrete vs. unbound
aggregates
• Similar void content for
emulsion and foamed bitumen
mixtures
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 14
0,0
5,0
10,0
15,0
20,0
25,0
30,0
A B C D E F G H
100%75% 50% 50% 40% - - -
- - 25% - 20% 50% 25% -
- 25% 25% 50% 40% 50% 75%100%
Vo
ids c
on
ten
t V
28
[%]
Bitumen emulsion
Foamed bitumen
Sample
RA
RRC
unb.
Results: Indirect tensile strength ITSdry after 28 days of curing (5 °C)
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 15
Foamed bitumen
Bitumen emulsion
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
A B C D E F G H
100%75% 50% 50% 40% - - -
- - 25% - 20% 50% 25% -
- 25% 25% 50% 40% 50% 75%100%
Ind
irect
ten
sile s
tren
gth
IT
Sd
ry(5°C
) [M
Pa] Bitumen emulsion
Foamed bitumen
RA
RRC
unb.
Results: Indirect tensile strength ITSdry after 28 days of curing (5 °C)
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 16
0,0
0,2
0,4
0,6
0,8
1,0
1,2
1,4
1,6
A B C D E F G H
100%75% 50% 50% 40% - - -
- - 25% - 20% 50% 25% -
- 25% 25% 50% 40% 50% 75%100%
Ind
irect
ten
sile s
tren
gth
IT
Sd
ry,2
8(5°C
) [M
Pa] Bitumen emulsion
Foamed bitumen
Sample
RA
RRC
unb.
• German specification:
• ITSdry,28 ≥ 0,75 MPa
• ITSdry,28 ≤ 1,2 MPa
• Mixtures with bitumen emulsion
show higher strength compared
to mixtures with foamed
bitumen
• Higher RA content results in
higher strength
• Lower void content
• Higher flexibility
• Increase of RRC compared to
unbound aggregates:
• Same strength in emulsionmixtures
• Higher strength in foamedbitumen mixtures
Water sensitivity: ITSdry/ITSwet [%] – 14 days water saturation at 20 °C
• Comparison between ITS of dry
cured specimen with saturate,
wet-cured specimen
• Emulsion mixtures:
• Little strength loss (~ -10 %)
• No effect of RA or RCC content
• Foamed bitumen
mixtures:
• For most mixtures strength increase (cement hydration)
• Strength decrease for mixtures with RRC – resulting from higher dry strengths
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 17
0
20
40
60
80
100
120
140
160
A B C D E F G H
100%75% 50% 50% 40% - - -
- - 25% - 20% 50% 25% -
- 25% 25% 50% 40% 50% 75%100%
Wate
r sen
sit
ivit
y:
Resid
ual
Str
en
gth
[%
]
Bitumen emulsion
Foamed bitumen
Sample
RA
RRC
unb.
Results: California Bearing Ratio CBRdry as indicator for resistance againstpermanent deformation (test temperature: 20 °C)
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 18
0
50
100
150
200
250
A B C D E F G H
100% 75% 50% 50% 40% - - -
- - 25% - 20% 50% 25% -
- 25% 25% 50% 40% 50% 75% 100%
Califo
rnia
Beari
ng
Rati
o C
BR
[%
]
Bitumen emulsion mixtures
Foamed bitumen mixtures
Sample
RA
RRC
Unb.
• Increase RA content results in
lower CBR-ratio (higher
deformation)
• RA bitumen is still „active“ in cold recycled mixtures
• RA flexibility results in deformation
• Foamed bitumen mixtures
indicate higher CBR (lower
deformation) compared to
emulsion mixtures
• Lower shear deformationbetween mix aggregates
• Better aggregate interlock
Discussions on limits regarding non-homogeneities of pavement structures:Void content requirements
• German specification for in-situ
control tests:
• Tolerance for void content compared to mix design: +4%
• Required RA content in actual
mix granulate (on site):
• Bitumen emulsion: 55 %
• Foamed bitumen: 65 %
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 19
R² = 0,9328
R² = 0,9532
14
16
18
20
22
24
26
28
30
0 50 100Vo
id c
on
ten
t o
f sp
ecim
en
s V
[%
]
RA content in mix granualte [%]
Bitumeninous emuslion mixtures
Foamed bitumen mixtures
Emulsion mix tolerance
Foamed bit. tolerance
+4 %
Bituminous emulsion mixtures
Discussions on limits regarding non-homogeneities of pavement structures:ITS requirements
• German specification for in-situ
control tests:
• Tolerance for ITS compared to mix design: -20 % (+ 30 %)
• Required RA content in actual
mix granulate (on site):
• Bitumen emulsion: 55 %
• Foamed bitumen: 70 %
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 20
R² = 0,9481
R² = 0,744
0
0,2
0,4
0,6
0,8
1
1,2
1,4
1,6
0 50 100
ITS
dry
(5 °
C)
[MP
a]
RA content in mix granualte [%]
Bitumeninous emuslion mixtures
Foamed bitumen mixtures
Emulsion mix tolerance
Foamed bit. tolerance
-20 %
Bituminous emulsion mixtures
• Conclusions valid for following cold recylcing mix
properties
• CBSM (foamed bitumen and bitumen emulsion)
• Residual bitumen content: 4 %
• Cement content: 2 %
• Same grading of mix granulate
• RA content in mix granulate is predominating
property
• Limit of allowed RA-content in mix granulate
• Bitumen emulsion mix: RA ≥ 55 %
• Foamed bitumen mix: RA ≥ 70 %
• Bitumen within RA is significantly “active” within
cold recycling mixtures
Conclusions regarding allowed tolerances on structural variability
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 21
• Assess pavement structure prior to recycling
works thoroughly:
• Assess structural history (locals)
• Coring for assessment of structure along the road with varying transversal positions
• Ensure best homogenisation of mix granulate:
• transversal mixing will reduce effects of varying structural properties
• Apply In-plant (cold) recycling
• In case of highly varying structural properties
• In case of high quality requirements (traffic loading)
Recommendations
Asphaltni Kolnici 2017 | Asphalt Pavements 2017 | Konrad Mollenhauer | 06.04.2017 | Opatija | 22
Transversal mixing
recommended
Hrvatsko asfaltersko društvo Croatian asphalt association
Hvala na pažnji
Thank you very muchfor your attention